Pressure sensing device and method of fabrication thereof

Abstract

The present disclosure concerns a pressure sensing device, comprising a pressure sensing layer comprising a first polymer layer and a second polymer layer, the first polymer layer comprising microstructures on a first surface thereof, the second polymer layer adjacent to the microstructures on the first surface; a transparent electrode layer configured to be electrically conductive; an electroluminescence layer comprising luminescent particles, the 10 electroluminescence layer sandwiched between the second polymer layer of the pressure sensing layer and the transparent electrode layer; wherein the pressure sensing layer is in electrical communication with the transparent electrode layer; wherein the microstructures are configured to be electrically responsive to changes in their morphologies; and wherein the electroluminescence layer is configured to provide an electroluminescence output and the transparent electrode layer is configured to produce a capacitance output in response to a pressure sensed at the pressure sensing layer. The present disclosure also concerns a method of fabricating a pressure sensing device.

Description

[0001]

[0002] Pressure Sensing Device and Method of Fabrication Thereof

[0003] Technical Field

[0004] The present invention relates, in general terms, to a pressure sensing device and the method of fabrication.

[0005] Background

[0006] Pressure mapping is widely used in various healthcare scenarios, including foot pressure mapping, which can aid in the diagnosis and treatment of various foot- related conditions.

[0007] Pressure sensing devices may be used for pressure mapping. Current foot pressure measurement products, such as pressure sensing mats and smart insoles, encounter certain challenges. These devices require bulky equipment and communication systems to acquire and interpret data, resulting in a costly and inconvenient platform for users. Additionally, they are limited in resolution for pressure mapping, as they can only achieve spatial pressure mapping through the use of a sensor array.

[0008] Electronic skin (E-skin) is a type of pressure sensing device. For example, an E- skin may utilize capacitive response in the low-pressure range and luminescent response in the high-pressure range. However, the need to switch detecting methods during usage limits its applications. Moreover, current e-skin can only apply luminescent response in the high-pressure range, which restricts its ability to visualize pressure mapping for small stimuli. An electroluminescent pressuresensing display has been proposed which allows for direct visualization of static and dynamic information of position, shape, and size of a pressurizing object on a single-device platform. However, the materials chosen for the display may limit its softness and stretchability, and the display resolution is not very high. Some e-skins have complex fabrication techniques and can only generate luminescent response, lacking the ability to quantitatively measure pressure.

[0009] It would be desirable to overcome or ameliorate at least one of the abovedescribed problems.

[0010] Summary

[0011] The present disclosure concerns a pressure sensing device, comprising : a) a pressure sensing layer comprising a first polymer layer and a second polymer layer, the first polymer layer comprising microstructures on a first surface thereof, the second polymer layer adjacent to the microstructures on the first surface; b) a transparent electrode layer configured to be electrically conductive; c) an electroluminescence layer comprising luminescent particles, the electroluminescence layer sandwiched between the second polymer layer of the pressure sensing layer and the transparent electrode layer; wherein the pressure sensing layer is in electrical communication with the transparent electrode layer; wherein the microstructures are configured to be electrically responsive to changes in their morphologies; and wherein the electroluminescence layer is configured to provide an electroluminescence output and the transparent electrode layer is configured to produce a capacitance output in response to a pressure sensed at the pressure sensing layer.

[0012] In some embodiments, the microstructures is an array of microdomes.

[0013] In some embodiments, the microstructures characterized by a diameter of about 10 pm to about 40 pm.

[0014] In some embodiments, the microstructures characterized by a diameter of about

[0015] In some embodiments, the microstructures are characterized by a height of about 5 m to about 30 pm.

[0016] In some embodiments, the microstructures are characterized by a height of about 15 pm.

[0017] In some embodiments, the microstructures are characterized by a spacing of about 5 pm to about 20 pm.

[0018] In some embodiments, the microstructures are characterized by a spacing of about 10 pm.

[0019] In some embodiments, the first polymer layer is formed from PDMS.

[0020] In some embodiments, the first polymer layer is characterized by a thickness of about 5 pm to about 250 pm.

[0021] In some embodiments, the first polymer layer is characterized by a thickness of about 10 pm.

[0022] In some embodiments, the second polymer layer is formed from a combination of PEDOT: PSS and PU.

[0023] In some embodiments, the combination of PEDOT: PSS and PU is characterized by a weight ratio of about 1 : 1 to about 3: 1.

[0024] In some embodiments, the combination of PEDOT: PSS and PU is characterized by a weight ratio of about 7:4.

[0025] In some embodiments, the first polymer layer is bonded to the second polymer layer via electrostatic and / or Van der Waals interaction.

[0026] In some embodiments, the first polymer layer is bonded to the second polymer layer via Van der Waals interaction.

[0027] In some embodiments, the second polymer layer is characterized by a thickness of about 500 nm to about 1000 nm.

[0028] In some embodiments, the second polymer layer is characterized by a thickness of about 800 nm.

[0029] In some embodiments, the pressure sensing layer further comprises metal nanowires.

[0030] In some embodiments, the metal nanowires are homogenously dispersed within the first polymer layer, homogenously dispersed within the second polymer layer or layered adjacent to the microstructures.

[0031] In some embodiments, the metal nanowires in the pressure sensing layer is characterized by a loading wt% of about 20 wt% to about 60 wt%.

[0032] In some embodiments, the metal nanowires in the pressure sensing layer is characterized by a loading wt% of about 40 wt%.

[0033] In some embodiments, the pressure sensing layer is characterized by a thickness of about 10 pm to about 280 pm.

[0034] In some embodiments, the pressure sensing layer is characterized by a thickness of about 10 pm.

[0035] In some embodiments, the transparent electrode layer comprises a third polymer layer and a fourth polymer layer adjacent to the third polymer layer.

[0036] In some embodiments, the third polymer layer is formed from PDMS.

[0037] In some embodiments, the third polymer layer is characterized by a thickness of about 5 pm to about 250 pm.

[0038] In some embodiments, the third polymer layer is characterized by a thickness of about 10 pm.

[0039] In some embodiments, the fourth polymer layer is formed from a combination of PEDOT: PSS / PU.

[0040] In some embodiments, the combination of PEDOT: PSS and PU is characterized by a weight ratio of about 1 : 1 to about 3: 1.

[0041] In some embodiments, the combination of PEDOT: PSS and PU is characterized by a weight ratio of about 7:4.

[0042] In some embodiments, the third polymer layer is bonded to the fourth polymer layer via electrostatic and / or Van der Waals interaction.

[0043] In some embodiments, the third polymer layer is bonded to the fourth polymer layer via Van der Waals interaction.

[0044] In some embodiments, the fourth polymer layer is characterized by a thickness of about 500 nm to about 1000 nm.

[0045] In some embodiments, the fourth polymer layer is characterized by a thickness of about 800 nm.

[0046] In some embodiments, the transparent electrode layer further comprises metal nanowires.

[0047] In some embodiments, the metal nanowires are homogenously dispersed within the third polymer layer, homogenously dispersed within the fourth polymer layer or layered adjacent to a surface of the third polymer layer.

[0048] In some embodiments, the metal nanowires are dispersed as a layer between the third polymer layer and the fourth polymer layer.

[0049] In some embodiments, the metal nanowires in the transparent electrode layer is characterized by a loading wt% of about 20 wt% to about 60 wt%.

[0050] In some embodiments, the metal nanowires in the transparent electrode layer is characterized by a loading wt% of about 40 wt%.

[0051] In some embodiments, the transparent electrode layer is characterized by a thickness of about 5 pm to about 250 pm.

[0052] In some embodiments, the transparent electrode layer is characterized by a thickness of about 10 pm.

[0053] In some embodiments, the electroluminescence layer further comprises a fluoroelastomer.

[0054] In some embodiments, the fluoroelastomer is PVDF.

[0055] In some embodiments, the luminescent particles are homogenously dispersed within the electroluminescence layer or layered adjacent to a surface of the electroluminescence layer.

[0056] In some embodiments, the luminescent particles is selected from ZnS:Cu, ZnS:Mn, ZnS:TbF3, ZnS:SmF3, CaS:Ce and their doped derivative thereof.

[0057] In some embodiments, the luminescent particles is ZnS:Cu.

[0058] In some embodiments, the electroluminescence layer is characterized by a luminescent particle concentration of about 25 wt% to about 75 wt%.

[0059] In some embodiments, the electroluminescence layer is characterized by a luminescent particle concentration of about 50 wt%.

[0060] In some embodiments, the electroluminescence layer is characterized by a thickness of about 40 pm to about 120 pm.

[0061] In some embodiments, the electroluminescence layer is characterized by a thickness of about 80 pm.

[0062] In some embodiments, the layers are adhesively bonded to each other.

[0063] In some embodiments, the pressure sensing layer and the transparent electrode layer are in electrical communication via wires.

[0064] In some embodiments, the microstructures are configured to deform under pressure.

[0065] In some embodiments, the capacitance output is characterized by a pressure of 0 kPa to about 180 kPa.

[0066] In some embodiments, the capacitance output response is characterized by a sensitivity between about 0.01 kPa1to about 0.05 kPa1when the pressure is 0 kPa to about 30 kPa.

[0067] In some embodiments, the capacitance output response is characterized by a sensitivity of about 0.001 kPa1to about 0.005 kPa-1when the pressure is about 30 kPa to about 180 kPa.

[0068] In some embodiments, the device is configured to be powered by an alternating current power supply of about 100 V to about 250 V.

[0069] In some embodiments, the device is configured to be powered by an alternating current power supply of about 150 V.

[0070] In some embodiments, the electroluminescence output is characterized by a frequency of 0 kHz to about 5 kHz.

[0071] In some embodiments, the electroluminescence output is characterized by a frequency of about 1 kHz.

[0072] In some embodiments, the electroluminescence output is characterized by a pressure of 0 kPa to about 180 kPa.

[0073] In some embodiments, the electroluminescence output is characterized by a sensitivity of about 1 kPa1to about 1.5 kPa1when the pressure is 0 kPa to about 30 kPa.

[0074] In some embodiments, the electroluminescence output is characterized by a sensitivity of about 0.1 kPa1to about 0.5 kPa1when the pressure is about 30 kPa to about 180 kPa.

[0075] In some embodiments, the device is characterized by a strain of about 30% to about 55%.

[0076] In some embodiments, the device is characterized by a strain of about 45%.

[0077] The present disclosure also concerns a method of fabricating a pressure sensing device as disclosed herein, the method comprising : a) bonding a pressure sensing layer to a surface of an electroluminescence layer such that a second polymer layer of the pressure sensing layer is contacted with the surface of the electroluminescence layer; b) bonding another surface of the electroluminescence layer with a transparent electrode layer such that the electroluminescence layer is sandwiched between the second polymer layer of the pressure sensing layer and the transparent electrode layer; and c) electrically communicating the pressure sensing layer and the transparent electrode layer.

[0078] In some embodiments, the bonding in step a) is performed using adhesive.

[0079] In some embodiments, the bonding in step b) is performed using adhesive.

[0080] In some embodiments, the pressure sensing layer and the transparent electrode layer are electrically communicated using a wire and / or metallic paste.

[0081] The present disclosure also concerns a method of detecting pressure, comprising : a) subjecting a pressure sensing device as disclosed herein to the pressure; and b) obtaining an electroluminescence output and / or capacitance output from the pressure sensing device.

[0082] Brief description of the drawings

[0083] Embodiments of the present invention will now be described, by way of nonlimiting example, with reference to the drawings in which:

[0084] Figure 1 shows a structure of the device.

[0085] Figure 2 shows a fabrication method of each component of the device.

[0086] Figure 3 shows the micromorphology of a pressure sensing layer.

[0087] Figure 4 shows SEM images of an electroluminescent layer and a transparent electrode.

[0088] Figure 5 shows capacitive response of the device.

[0089] Figure 6 shows response time of capacitance response. When a pressure is applied, the response time is about 110 ms for 0 AC / Co to go to 0.3 AC / Co, and when recovery, the response time is about 150 ms for 0.3 AC / Co to go to 0 AC / Co.

[0090] Figure 7 shows cycle stability test.

[0091] Figure 8 shows electroluminescent intensity of the device when applied with increasing frequency of AC power supply.

[0092] Figure 9 shows luminescent intensity of the device with various voltage of power supply and applied pressure.

[0093] Figure 10 shows response time of luminescent response.

[0094] Figure 11 shows pressure mapping resolution of the device.

[0095] Figure 12 shows real-time dynamic pressure visualisation.

[0096] Figure 13 shows real-time pressure mapping of a fingerprint.

[0097] Figure 14 shows schematic illustration of foot pressure mapping with device. Figure 15 shows a demonstration of foot pressure mapping using the device. Figure 16 shows the stretchability of the device.

[0098] Detailed description

[0099] The present disclosure concerns a pressure-sensitive device that integrates dual-mode capacitive and electroluminescent responses for on-the-spot pressure imaging and tactile sensing. The device demonstrates a broad sensing range with two linear regions, ensuring linearity and sensitivity in both sensing modes. The device may be capable of capturing intricate patterns, such as fingerprints, with high spatial resolution for pressure mapping. The device may maintain flexibility through a convenient fabrication method and may maintain sensing performance after bending cycles.

[0100] The device may have a high resolution and be flexible. The device may be used to replicate the pressure-sensing abilities of human skin, functioning as an e- skin or a system that translates pressure stimuli into visible optical signals. The intensity of luminescence may be configured to correspond to the magnitude and location of the applied pressure. This not only enables foot pressure mapping for diabetic patients but may also be used in medical training. It may guide doctors and nurses by indicating the appropriate amount of pressure to apply during procedures like blood blocking, needle insertion, compression bandage therapy, and more. This may assist in the formulation of effective prevention and treatment plans.

[0101] The presently disclosed device is also electroluminescent, and hence offers realtime pressure visualization. By leveraging electroluminescence, the device enables precise and high-resolution pressure visualization without the need for bulky devices or complex communication systems. This feature addresses the drawbacks of existing products by providing a user-friendly and cost-effective alternative.

[0102] Accordingly, the present disclosure concerns a pressure sensing device, comprising : a) a pressure sensing layer comprising a first polymer layer and a second polymer layer, the first polymer layer comprising microstructures on a first surface thereof, the second polymer layer adjacent to the microstructures on the first surface; b) a transparent electrode layer configured to be electrically conductive; c) an electroluminescence layer comprising luminescent particles, the electroluminescence layer sandwiched between the second polymer layer of the pressure sensing layer and the transparent electrode layer; wherein the pressure sensing layer is in electrical communication with the transparent electrode layer; wherein the microstructures are configured to be electrically responsive to changes in their morphologies; and wherein the electroluminescence layer is configured to provide an electroluminescence output and the transparent electrode layer is configured to produce a capacitance output in response to a pressure sensed at the pressure sensing layer.

[0103] The electrode layer may work together with the pressure sensing layer, of which they are separated by the electroluminescence layer, to provide the capacitance output.

[0104] The device is easy to use and eliminates the need for expensive and bulky pressure senor arrays, as well as complex communication and interpretation systems, to visualize pressure mapping. The device is capable of dual-mode sensing and is multi-functional, possessing the capability to acquire electrical and visual optical signals and making it versatile for various applications. The device may serve as a tool to visually alert patients with peripheral nerve dysfunction about abnormal pressure, aiding in the prevention of ulcers. It may also function as a warning system for biomimetic robots or individuals with amputations, notifying them of high-risk, high-pressure situations. Additionally, the device is capable of detecting both static pressure and dynamic tactile tracks, further expanding its functionality. The device may have high spatial resolution to visualize minute pressure patterns, including intricate details like fingerprints. The device may be flexible and may be applied on curved structures such as human skin. The flexibility allows the device to conform and adhere to curved surfaces and may enable seamless integration and accurate pressure sensing on different contours.

[0105] As shown in Figure 1, the device comprises of three layers - a pressure sensing layer, a transparent electrode and an electroluminescence layer. The layers may be adhesively bonded to each other. Alternatively, the layers may be laminated to each other. The pressure sensing layer comprises a first polymer layer and a second polymer layer. The first polymer layer comprises microstructures on a first surface thereof and the second polymer layer is adjacent to the microstructures on the first surface. The microstructures may be an array of microdomes (Figure 3). The microstructures are configured to be electrically responsive to changes in their morphologies. The rebound resilience of the pressure sensing layer may increase the stability and response time of the microstructures to changes in their morphologies.

[0106] In some embodiments, the microstructures characterized by a diameter of about 10 pm to about 40 pm. In other embodiments, the diameter is about 10 pm to about 35 pm, about 10 pm to about 30 pm, about 10 pm to about 25 pm, about 10 pm to about 20 pm, or about 15 pm to about 20 pm. In other embodiments, the diameter is about 20 pm.

[0107] In some embodiments, the microstructures are characterized by a height of about 5 pm to about 30 pm. In other embodiments, the height is about 5 pm to about 25 pm, about 5 pm to about 20 pm, about 5 pm to about 15 pm, about 10 pm to about 30 pm, about 10 pm to about 20 pm, or about 15 pm to about 30 pm. In other embodiments, the height is about 15 pm.

[0108] In some embodiments, the microstructures are characterized by a spacing of about 5 pm to about 20 pm. In this sense, the microstructures are spaced apart (length-wise and / or width-wise) from each other by about 5 pm to about 20 pm. In other embodiments, the spacing is about 5 pm to about 15 pm, about 5 pm to about 10 pm, or about 10 pm to about 20 pm. In other embodiments, the spacing is about 10 pm.

[0109] In some embodiments, the first polymer layer of the pressure sensing layer is formed from poly(dimethylsiloxane) (PDMS), polyvinylidene fluoride (PVDF), polyaniline (PANI), or a combination thereof. In some embodiments, the polymer is PDMS. For example, the first polymer layer may be formed from a PDMS mixture consisting of a base and a curing agent at a w / w ratio of about 10: 1. The PDMS mixture may be cured at about 70 °C for about 4 hours to form a PDMS film comprising microstructures.

[0110] In some embodiments, the microstructures are configured to deform under pressure. The stiffness of the microstructures may be the same stiffness as the first polymer layer and / or second polymer layer of the pressure sensing layer. For example, the microstructures may have the same stiffness as the PDMS layer. When pressure is applied, the microstructures are compressed and at least partially deformed, reducing the height of the microstructures. This increases the contact area between the microstructures and the electroluminescent layer and / or electrode layer.

[0111] In some embodiments, the microstructure is characterized by a stiffness of about 0.8 MPa to about 10 MPa. For example, if the microstructures are formed using PDMS, the stiffness of PDMS may be varied by varying PDMS to the curing agent base ratio over 19: 1 to 2: 1. In other embodiments, the stiffness is about 1 MPa to about 10 MPa, about 1.5 MPa to about 10 MPa, about 2 MPa to about 10 MPa, about 2.5 MPa to about 10 MPa, about 3 MPa to about 10 MPa, about 3.5 MPa to about 10 MPa, about 4 MPa to about 10 MPa, about 4.5 MPa to about 10 MPa, about 5 MPa to about 10 MPa, about 5.5 MPa to about 10 MPa, about 6 MPa to about 10 MPa, about 6.5 MPa to about 10 MPa, about 7 MPa to about 10 MPa, about 7.5 MPa to about 10 MPa, or about 8 MPa to about 10 MPa.

[0112] In some embodiments, the thickness of the first polymer layer is about 5 pm to about 250 pm. In other embodiments, the thickness is about 5 pm to about 200 pm, about 5 pm to about 150 pm, about 5 pm to about 100 pm, about 5 pm to about 50 pm, about 10 pm to about 250 pm, about 10 pm to about 200 pm, about 10 pm to about 150 pm, about 10 pm to about 100 pm, about 20 pm to about 250 pm, about 20 pm to about 200 pm, about 20 pm to about 150 pm, about 20 pm to about 100 pm, about 30 pm to about 250 pm, about 30 pm to about 200 pm, about 30 pm to about 150 pm, about 30 pm to about 100 pm, about 50 pm to about 250 pm, about 50 pm to about 200 pm, about 50 pm to about 150 pm, or about 50 pm to about 100 pm. In other embodiments, the thickness is about 10 pm.

[0113] In some embodiments, the second polymer layer is formed from a combination of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and polyurethane (PU).

[0114] The second polymer layer of PEDOT:PSS and PU enhances conductivity and flexibility of the pressure sensing layer with the formation of a hybrid conductive film.

[0115] The polymers as used herein also includes their derivatives thereof. For example, polydiphenylsiloxane, polydibenzylsiloxane, polydiethylenesiloxane, polyvinyldiene fluoride-trifluoroethylene, polyalkylaniline, polyalkoxyaniline and hydroxymethly-PEDOT.

[0116] In some embodiments, the combination of PEDOT:PSS and PU is characterized by a weight ratio of about 1:1 to about 3:1. In other embodiments, the ratio is about 1:1 to about 11:4, about 1:1 to about 5:2, about 1:1 to about 9:4, about 1:1 to about 2:1, about 1:1 to about 7:4, about 1:1 to about 3:2, about 1:1 to about 5:4, about 5:4 to about 3:1, about 5:4 to about 11:4, about 5:4 to about 5:2, about 5:4 to about 9:4, about 5:4 to about 2:1, about 5:4 to about 7:4, about 5:4 to about 3:2, about 3:2 to about 3:1, about 3:2 to about 11:4, about 3:2 to about 5:2, about 3:2 to about 9:4, about 3:2 to about 2:1, about 3:2 to about 7:4, about 7:4 to about 3:1, about 7:4to about 11:4, about 7:4 to about 5:2, about 7:4 to about 9:4, about 7:4 to about 2:1, about 2:1 to about 3:1, about 2: 1 to about 11:4, about 2: 1 to about 5:2, about 2: 1 to about 9:4, about 9:4 to about 3:1, about 9:4 to about 11:4, about 9:4 to about 5:2, about 5:2 to about 3:1, or about 5:2 to about 11:4. In other embodiments, the ratio is about 7:4.

[0117] In some embodiments, the PEDOT:PSS in the polymer layer is characterized by a weight percent of about 40 wt% to about 80 wt%. In other embodiments, the weight percent is about 40 wt% to about 75 wt%, about 40 wt% to about 70 wt%, about 40 wt% to about 65 wt%, about 40 wt% to about 60 wt%, about 40 wt% to about 55 wt%, about 40 wt% to about 50 wt%, about 50 wt% to about 80 wt%, about 50 wt% to about 75 wt%, about 50 wt% to about 70 wt%, about 50 wt% to about 65 wt%, about 50 wt% to about 50 wt%, about 50 wt% to about 55 wt%, about 55 wt% to about 80 wt%, about 55 wt% to about 75 wt%, about 55 wt% to about 70 wt%, about 55 wt% to about 65 wt%, about 55 wt% to about 60 wt%, about 60 wt% to about 80 wt%, about 60 wt% to about 75 wt%, about 60 wt% to about 70 wt%, about 60 wt% to about 65 wt%, about 65 wt% to about 80 wt%, about 65 wt% to about 75 wt%, about 65 wt% to about 70 wt%, about 70 wt% to about 80 wt%, or about 70 wt% to about 75 wt%. In other embodiments, the weight percent is about 64 wt%.

[0118] In some embodiments, the PU in the polymer layer is characterized by a weight percent of about 20 wt% to about 60 wt%. In other embodiments, the weight percent is about 20 wt% to about 50 wt%, about 20 wt% to about 45 wt%, about 20 wt% to about 40 wt%, about 20 wt% to about 35 wt%, about 20 wt% to about 30 wt%, about 20 wt% to about 25 wt%, about 25 wt% to about 60 wt%, about 25 wt% to about 50 wt%, about 25 wt% to about 45 wt%, about 25 wt% to about 40 wt%, about 25 wt% to about 35 wt%, about 25 wt% to about 30 wt%, about 30 wt% to about 60 wt%, about 30 wt% to about 50 wt%, about 30 wt% to about 45 wt%, about 30 wt% to about 40 wt%, about 30 wt% to about 35 wt%, about 35 wt% to about 60 wt%, about 35 wt% to about 50 wt%, about 35 wt% to 45 wt%, about 35 wt% to about 40 wt%, about 40 wt% to about 60 wt%, about 40 wt% to about 50 wt%, about 40 wt% to about 45 wt%, about 45 wt% to about 60 wt%, about 45 wt% to about 50 wt% or about 50 wt% to about 60 wt%. In other embodiments, the weight percent is about 36 wt%.

[0119] In some embodiments, PEDOT:PSS relative to PEDOT:PSS and PU is characterized by a weight percent of about 40 wt% to about 80 wt%. In other embodiments, the weight percent is about 40 wt% to about 75 wt%, about 40 wt% to about 70 wt%, about 40 wt% to about 65 wt%, about 40 wt% to about 60 wt%, about 40 wt% to about 55 wt%, about 40 wt% to about 50 wt%, about 50 wt% to about 80 wt%, about 50 wt% to about 75 wt%, about 50 wt% to about 70 wt%, about 50 wt% to about 65 wt%, about 50 wt% to about 50 wt%, about 50 wt% to about 55 wt%, about 55 wt% to about 80 wt%, about 55 wt% to about 75 wt%, about 55 wt% to about 70 wt%, about 55 wt% to about 65 wt%, about 55 wt% to about 60 wt%, about 60 wt% to about 80 wt%, about 60 wt% to about 75 wt%, about 60 wt% to about 70 wt%, about 60 wt% to about 65 wt%, about 65 wt% to about 80 wt%, about 65 wt% to about 75 wt%, about 65 wt% to about 70 wt%, about 70 wt% to about 80 wt%, or about 70 wt% to about 75 wt%. In other embodiments, the weight percent is about 64 wt%.

[0120] In some embodiments, the first polymer layer is bonded to the second polymer layer via electrostatic interaction and / or Van der Waals interaction. In other embodiments, the interaction is Van der Waals interaction.

[0121] In some embodiments, the thickness of the second polymer layer is about 500 nm to about 1000 nm. In other embodiments, the thickness is about 500 nm to about 900 nm, about 500 nm to about 800 nm, about 600 nm to about 1000 nm, about 600 nm to about 900 nm, about 600 nm to about 800 nm, about 700 nm to about 1000 nm, about 700 nm to about 900 nm, or about 700 nm to about 800 nm. In other embodiments, the thickness is 800 nm.

[0122] In some embodiments, the pressure sensing layer acts as an opposing electrode to the transparent electrode layer. Towards this end, the pressure sensing layer may comprise an electrically conducting polymer or material. When the two electrodes of the device are connected to a multimeter, it performs digital capacitive pressure sensing.

[0123] In some embodiments, the pressure sensing layer further comprises metal nanowires. In some embodiments, the pressure sensing layer further comprises gold and / or silver nanowires. The metal nanowires may be homogenously dispersed within the first polymer layer, homogenously dispersed within the second polymer layer or layered adjacent to the microstructures. Layering the nanowires on the microstructures may increase its surface roughness, thereby improving its pressure sensing capability. The metal nanowires form a conductive network in the pressure sensing layer, thus allowing the pressure sensing layer to be electrically conductive. The metal nanowires may be protected from oxidation by the polymer layers. In combination with the electrode layer, the metal nanowires may provide localized electric output in response to a pressure.

[0124] In some embodiments, the metal nanowires in the pressure sensing layer is characterized by a loading wt% of about 20 wt% to about 60 wt%. In other embodiments, the loading wt% is about 20 wt% to about 50 wt%, about 20 wt% to about 40 wt%, about 30 wt% to about 60 wt%, about 30 wt% to about 50 wt%, or about 30 wt% to about 40 wt%. In other embodiments, the loading wt% is about 40 wt%.

[0125] In some embodiments, the pressure sensing layer is characterized by a thickness of about 10 pm to 280 pm. In other embodiments, the thickness is about 10 pm to 250 pm, about 10 pm to 200 pm, about 10 pm to 150 pm, about 10 pm to 100 pm, about 10 pm to 50 pm, about 20 pm to 280 pm, about 20 pm to 250 pm, about 20 pm to 200 pm, about 20 pm to 150 pm, about 20 pm to 100 pm, about 20 pm to 50 pm, about 50 pm to 280 pm, about 50 pm to 250 pm, about 50 pm to 200 pm, about 50 pm to 150 pm, or about 50 pm to 100 pm. In other embodiments, the thickness is 10 pm.

[0126] The transparent electrode layer is configured to be electrically conductive. In some embodiments, the transparent electrode layer comprises a third polymer layer and a fourth polymer layer adjacent to the third polymer layer.

[0127] In some embodiments, the third layer is formed from PDMS.

[0128] In some embodiments, the thickness of the layer is about 5 pm to about 250 pm. In other embodiments, the thickness is about 5 pm to about 200 pm, about 5 pm to about 150 pm, about 5 pm to about 100 pm, about 5 pm to about

[0129] 50 pm, about 10 pm to about 250 pm, about 10 pm to about 200 pm, about 10 pm to about 150 pm, about 10 pm to about 100 pm, about 20 pm to about 250 pm, about 20 pm to about 200 pm, about 20 pm to about 150 pm, about 20 pm to about 100 pm, about 30 pm to about 250 pm, about 30 pm to about 200 pm, about 30 pm to about 150 pm, about 30 pm to about 100 pm, about 50 pm to about 250 pm, about 50 pm to about 200 pm, about 50 pm to about 150 pm, or about 50 pm to about 100 pm. In other embodiments, the thickness is about 10 pm.

[0130] In some embodiments, the fourth polymer layer is formed from a combination of PEDOT:PSS and PU.

[0131] The fourth polymer layer of PEDOT:PSS and PU enhances conductivity and flexibility of the transparent electrode layer with the formation of a hybrid conductive film.

[0132] In some embodiments, the combination of PEDOT:PSS and PU is characterized by a weight ratio of about 1: 1 to about 3: 1. In other embodiments, the ratio is about 1: 1 to about 11 :4, about 1 : 1 to about 5:2, about 1: 1 to about 9:4, about 1: 1 to about 2: 1, about 1: 1 to about 7:4, about 1 : 1 to about 3:2, about 1: 1 to about 5:4, about 5:4 to about 3: 1, about 5:4 to about 11:4, about 5:4 to about 5:2, about 5:4 to about 9:4, about 5:4 to about 2: 1, about 5:4 to about 7:4, about 5:4 to about 3:2, about 3:2 to about 3:1, about 3:2 to about 11:4, about 3:2 to about 5:2, about 3:2 to about 9:4, about 3:2 to about 2: 1, about 3:2 to about 7:4, about 7:4 to about 3: 1, about 7:4 to about 11:4, about 7:4 to about 5:2, about 7:4 to about 9:4, about 7:4 to about 2: 1, about 2: 1 to about 3: 1, about 2: 1 to about 11 :4, about 2: 1 to about 5:2, about 2: 1 to about 9:4, about 9:4 to about 3:1, about 9:4 to about 11:4, about 9:4 to about 5:2, about 5:2 to about 3: 1, or about 5:2 to about 11:4. In other embodiments, the ratio is about 7:4.

[0133] In some embodiments, the PEDOT:PSS in the polymer layer is characterized by a weight percent of about 40 wt% to about 80 wt%. In other embodiments, the weight percent is about 40 wt% to about 75 wt%, about 40 wt% to about 70 wt%, about 40 wt% to about 65 wt%, about 40 wt% to about 60 wt%, about 40 wt% to about 55 wt%, about 40 wt% to about 50 wt%, about 50 wt% to about 80 wt%, about 50 wt% to about 75 wt%, about 50 wt% to about 70 wt%, about 50 wt% to about 65 wt%, about 50 wt% to about 50 wt%, about 50 wt% to about 55 wt%, about 55 wt% to about 80 wt%, about 55 wt% to about 75 wt%, about 55 wt% to about 70 wt%, about 55 wt% to about 65 wt%, about 55 wt% to about 60 wt%, about 60 wt% to about 80 wt%, about 60 wt% to about 75 wt%, about 60 wt% to about 70 wt%, about 60 wt% to about 65 wt%, about 65 wt% to about 80 wt%, about 65 wt% to about 75 wt%, about 65 wt% to about 70 wt%, about 70 wt% to about 80 wt%, or about 70 wt% to about 75 wt%. In other embodiments, the weight percent is about 64 wt%.

[0134] In some embodiments, the PU in the polymer layer is characterized by a weight percent of about 20 wt% to about 60 wt%. In other embodiments, the weight percent is about 20 wt% to about 50 wt%, about 20 wt% to about 45 wt%, about 20 wt% to about 40 wt%, about 20 wt% to about 35 wt%, about 20 wt% to about 30 wt%, about 20 wt% to about 25 wt%, about 25 wt% to about 60 wt%, about 25 wt% to about 50 wt%, about 25 wt% to about 45 wt%, about 25 wt% to about 40 wt%, about 25 wt% to about 35 wt%, about 25 wt% to about 30 wt%, about 30 wt% to about 60 wt%, about 30 wt% to about 50 wt%, about 30 wt% to about 45 wt%, about 30 wt% to about 40 wt%, about 30 wt% to about 35 wt%, about 35 wt% to about 60 wt%, about 35 wt% to about 50 wt%, about 35 wt% to 45 wt%, about 35 wt% to about 40 wt%, about 40 wt% to about 60 wt%, about 40 wt% to about 50 wt%, about 40 wt% to about 45 wt%, about 45 wt% to about 60 wt%, about 45 wt% to about 50 wt% or about 50 wt% to about 60 wt%. In other embodiments, the weight percent is about 36 wt%.

[0135] In some embodiments, PEDOT:PSS relative to PEDOT:PSS and PU is characterized by a weight percent of about 40 wt% to about 80 wt%. In other embodiments, the weight percent is about 40 wt% to about 75 wt%, about 40 wt% to about 70 wt%, about 40 wt% to about 65 wt%, about 40 wt% to about 60 wt%, about 40 wt% to about 55 wt%, about 40 wt% to about 50 wt%, about 50 wt% to about 80 wt%, about 50 wt% to about 75 wt%, about 50 wt% to about 70 wt%, about 50 wt% to about 65 wt%, about 50 wt% to about 50 wt%, about 50 wt% to about 55 wt%, about 55 wt% to about 80 wt%, about 55 wt% to about 75 wt%, about 55 wt% to about 70 wt%, about 55 wt% to about 65 wt%, about 55 wt% to about 60 wt%, about 60 wt% to about 80 wt%, about 60 wt% to about 75 wt%, about 60 wt% to about 70 wt%, about 60 wt% to about 65 wt%, about 65 wt% to about 80 wt%, about 65 wt% to about 75 wt%, about 65 wt% to about 70 wt%, about 70 wt% to about 80 wt%, or about 70 wt% to about 75 wt%. In other embodiments, the weight percent is about 64 wt%.

[0136] In some embodiments, the third polymer layer is bonded to the fourth polymer layer via electrostatic interaction and / or Van der Waals interaction. In other embodiments, the interaction is Van der Waals interaction.

[0137] In some embodiments, the thickness of the fourth polymer layer is about 200 nm to about 1000 nm. In other embodiments, the thickness is about 300 nm to about 1000 nm, about 400 nm to about 1000 nm, about 500 nm to about 1000 nm, about 500 nm to about 900 nm, about 500 nm to about 800 nm, about 600 nm to about 1000 nm, about 600 nm to about 900 nm, about 600 nm to about 800 nm, about 700 nm to about 1000 nm, about 700 nm to about 900 nm, or about 700 nm to about 800 nm. In other embodiments, the thickness is 800 nm.

[0138] In some embodiments, the transparent electrode layer further comprises metal nanowires. The metal nanowires may be dispersed within the transparent electrode layer, homogenously dispersed within the fourth polymer layer or dispersed as a layer adjacent to a surface of the transparent electrode layer.

[0139] In some embodiments, the metal nanowires are dispersed as a layer between the third polymer layer and the fourth polymer layer. The metal nanowires may be gold and / or silver nanowires. For example, a silver nanowires / PEDOT: PSS / PU film formed on a silicone rubber substrate may form a well-fabricated conductive layer where the silver nanowires are well connected to form a conductive network, and PEDOT: PSS / PU fills the interspaces to increase conductivity, as shown in Figure 4b.

[0140] In some embodiments, the silver nanowires in the transparent electrode layer is characterized by a loading wt% of about 20 wt% to about 60 wt%. In other embodiments, the loading wt% is about 20 wt% to about 50 wt%, about 20 wt% to about 40 wt%, about 30 wt% to about 60 wt%, about 30 wt% to about 50 wt%, or about 30 wt% to about 40 wt%. In other embodiments, the loading wt% is about 40 wt%.

[0141] In some embodiments, the transparent electrode layer is characterized by a thickness of about 5 pm to 250 pm. In other embodiments, the thickness is about 5 pm to about 200 pm, about 5 pm to about 150 pm, about 5 pm to about 100 pm, about 5 pm to about 50 pm, about 10 pm to about 250 pm, about 10 pm to about 200 pm, about 10 pm to about 150 pm, about 10 pm to about 100 pm, about 20 pm to about 250 pm, about 20 pm to about 200 pm, about 20 pm to about 150 pm, about 20 pm to about 100 pm, about 30 pm to about 250 pm, about 30 pm to about 200 pm, about 30 pm to about 150 pm, about 30 pm to about 100 pm, about 50 pm to about 250 pm, about 50 pm to about 200 pm, about 50 pm to about 150 pm, or about 50 pm to about 100 pm. In other embodiments, the thickness is 10 pm.

[0142] The electroluminsence layer is sandwiched between the second polymer layer of the pressure sensing layer and the transparent electrode layer. In this regard, microstructures are inward facing and not exposed. The middle electroluminescent layer also functions as a dielectric, enabling the device to be considered a capacitor.

[0143] In some embodiments, the electroluminescence layer further comprises a fluoroelastomer. In some embodiments, the fluoroelastomer is PVDF.

[0144] The electroluminescence layer comprises luminescent particles. Luminescent particles emits light when exposed to radiant energy. Luminescent particles refers to both fluorescent particles and phosphorescent particles. Fluorescent particles emits light immediately when exposed to radiant energy and stop emitting light when the radiant energy is removed. Phosphorescent particles emit light after a delay when exposed to radiant energy and continues to emit light after the radiant energy is removed, decaying in brightness over a period of milliseconds to days.

[0145] As used herein, "luminescent particles" refers to nanoparticles and / or microsized particles that are capable of luminescence. In particular, micro-sized particles are preferred. It is believed that the micro-sized particles provide greater long-term stability and hence usability to the device.

[0146] In some embodiments, the luminescent particles are characterized by a particle size of about 5 pm to about 25 pm. In other embodiments, the particle size is about 5 pm to about 20 pm, about 5 pm to about 15 pm, about 5 pm to about 10 pm, about 10 pm to about 25 pm, about 10 pm to about 20 pm, about 15 pm to about 25 pm or about 15 pm to about 20 pm. In other embodiments, the particle size is about 10 pm to about 15 pm.

[0147] In some embodiments, the luminescent particles are homogenously dispersed within the electroluminescence layer or layered adjacent to a surface of the electroluminescence layer.

[0148] In some embodiments, the luminescent particles are phosphorescent particles. The phosphorescent particles may be ZnS:Cu, ZnS: Mn, ZnS:TbFa, ZnS:SmFa, CaS:Ce or their doped derivative thereof. In some embodiments, the luminescent particles is ZnS:Cu.

[0149] In some embodiments, the electroluminescence layer is characterized by a luminescent particle concentration of about 25 wt% to about 75 wt%. In other embodiments, the concentration is about 25 wt% to about 60 wt%, about 25 wt% to about 50 wt%, about 30 wt% to about 75 wt%, about 30 wtw% to about 6t0 %, about 30 wt% to about 50 wt%, about 40 wt% to about 75 wt%, about 40 wt% to about 60 wt%, about 40 wt% to about 50 wt%, about 50 wt% to about 75 wt%, or about 50 wt% to about 60 wt%. In other embodiments, the concentration is about 50 wt%.

[0150] In some embodiments, the electroluminescence layer is characterized by a thickness of about 40 pm to about 120 pm. In other embodiments, the thickness is about 40 pm to about 100 pm, about 40 pm to about 80 pm, about 50 pm to about 120 pm, about 50 pm to about 100 pm, about 50 pm to about 80 pm, about 60 pm to about 120 pm, about 60 pm to about 100 pm, about 60 pm to about 80 pm, about 70 pm to about 120 pm, about 70 pm to about 100 pm, about 70 pm to about 80 pm, about 80 pm to about 120 pm, or about 80 pm to about 100 pm. In other embodiments, the thickness is about 80 pm.

[0151] In some embodiments, the layers are adhesively bonded to each other.

[0152] The pressure sensing layer is in electrical communication with the transparent electrode layer. In some embodiments, the electrical communication is via wires. For example, copper wires are connected to the pressure sensing layer and transparent electrode using silver paste. In this sense, the pressure sensing layer acts as an electrode while the transparent electrode layer acts as another electrode. These layers are separated by an electrically non-conducting electroluminescence layer.

[0153] The transparent electrode layer is configured to produce a capacitance output in response to a pressure sensed at the pressure sensing layer. The deformation of the microstructures on the pressure sensing layer when pressure is applied results in an increased in contact area and a decrease in distance between the pressure sensing layer and the transparent electrode layer. The capacitance output changes in response to the changes in contact area and distance between the pressure sensing layer and the transparent electrode layer. The capacitance output may cause the luminescent particles in the electroluminescence layer to generate luminescence at different intensities relative to the separation distance.

[0154] In some embodiments, the capacitance output is characterized by a pressure of 0 kPa to about 180 kPa. In other embodiments, the pressure is 0 kPa to about 150 kPa, 0 kPa to about 100 kPa, 0 kPa to about 50 kPa, about 10 kPa to about 180 kPa, about 10 kPa to about 150 kPa, about 10 kPa to about 100 kPa, about 10 kPa to about 50 kPa, about 30 kPa to about 180 kPa, about 30 kPa to about 150 kPa, about 30 kPa to about 100 kPa, about 30 kPa to about 50 kPa, , about 50 kPa to about 180 kPa, about 50 kPa to about 150 kPa, about 50 kPa to about 100 kPa, about 100 kPa to about 180 kPa, or about 100 kPa to about 150 kPa. In other embodiments, the pressure is 0 kPa to about 30 kPa. In other embodiments, the pressure is about 30 kPa to about 180 kPa.

[0155] In some embodiments, the capacitance output response is characterized by a sensitivity of about 0.001 kPa1to about 0.050 kPa1. In other embodiments, the sensitivity is about 0.001 kPa-1to about 0.010 kPa-1, about 0.001 kPa-1to about 0.005 kPa-1, about 0.005 kPa-1to about 0.050 kPa-1, about 0.005 kPa-1to about 0.010 kPa-1, or about 0.010 kPa-1to about 0.050 kPa-1.

[0156] In some embodiments, when the sensed pressure is about 30 kPa to about 180 kPa, the device's capacitance output response is characterized by a sensitivity is about 0.001 kPa-1to about 0.005 kPa-1. In other embodiments, the sensitivity is about 0.001 kPa1to about 0.004 kPa1, about 0.001 kPa1to about 0.003 kPa' \ about 0.001 kPa-1to about 0.002 kPa-1, about 0.002 kPa-1to about 0.005 kPa' \ about 0.002 kPa-1to about 0.004 kPa-1, about 0.002 kPa-1to about 0.003 kPa'

[0157] \ about 0.003 kPa1to about 0.005 kPa1, about 0.003 kPa1to about 0.004 kPa- \ or about 0.004 kPa-1to about 0.005 kPa-1. In other embodiments, the sensitivity is about 0.002 kPa-1.

[0158] In some embodiments, when the sensed pressure is about 0 kPa to about 30 kPa, the device's capacitance output response is characterized by a sensitivity of about 0.01 kPa-1to about 0.05 kPa-1. In other embodiments, the sensitivity is about 0.01 kPa-1to about 0.04 kPa-1, about 0.01 kPa-1to about 0.03 kPa-1, about 0.01 kPa1to about 0.02 kPa-1, about 0.02 kPa1to about 0.05 kPa1, about 0.02 kPa-1to about 0.04 kPa-1, about 0.02 kPa-1to about 0.03 kPa-1, about 0.03 kPa-1to about 0.05 kPa-1, about 0.03 kPa-1to about 0.04 kPa-1, or about 0.04 kPa-1to about 0.05 kPa-1. In other embodiments, the sensitivity is about 0.011 kPa1.

[0159] The electroluminescence layer is configured to provide an electroluminescence output in response to a pressure sensed at the pressure sensing layer. For example, particles such as ZnS:Cu are capable of generating luminescence that is proportional to the local electric field intensity when connected to a high voltage alternating current (AC) supply. The deformation of the microstructures on the pressure sensing layer when pressure is applied results in a decrease in distance between the pressure sensing layer and the transparent electrode. This results in an increase in the electric field intensity. The electroluminescence response changes in response to the change in electric field intensity resulting from varying pressure applied on the pressure sensing layer.

[0160] For example, a PVDF electroluminescent layer with embedded ZnS:Cu phosphor particles forms a uniform and elastic film (Figure 4a). The porous structure of the PVDF substrate contributes to a significant change in capacitance when pressure is applied, resulting in enhanced mechanical sensitivity.

[0161] When a patterned pressure is exerted on the non-conductive side of the pressure sensing layer, the pressure distribution may be transferred between the pressure sensing layer and the electroluminescent layer, leading to an increase in electrical field and the intensity of luminescence at the pressure applying site. A thinner pressure sensing layer may have a higher resolution than a thicker sensing layer.

[0162] In some embodiments, the device is configured to be powered by an alternating current power supply of about 100 V to about 250 V. In other embodiments, the power supply is about 100 V to about 200 V, about 100 V to about 150 V, about 150 V to about 250 V, or about 150 V to about 200 V. In other embodiments, the power supply is about 150 V.

[0163] The frequency of the power supply, in addition to the voltage and applied pressure, also plays a role in influencing the intensity of electroluminescence (Figure 8). For example, when the voltage is fixed at 100 V and the pressure is maintained at 30 kPa, the luminescent intensity increases as the frequency is raised from 0 to 5 kHz. When the frequency is increased from 0 to 1 kHz, the luminescent intensity shows a significant increase, as shown in Figure 8. However, beyond 1 kHz, the rate of increase in luminescent intensity is relatively lower. 0-1 kHz may be chosen as the optimal working frequency for the device as the rate of change of luminescent is more significant while maintaining a balance between power consumption and noise levels.

[0164] In some embodiments, the electroluminescence output is characterized by a frequency of 0 kHz to about 5 kHz. In other embodiments, the frequency is 0 kHz to about 4 kHz, 0 kHz to about 3 kHz, 0 kHz to about 2 kHz, 0 kHz to about 1 kHz, about 1 kHz to about 5 kHz, about 1 kHz to about 4 kHz, about 1 kHz to about 3 kHz, about 1 kHz to about 2 kHz, about 2 kHz to about 5 kHz, about 2 kHz to about 4 kHz, about 2 kHz to about 3 kHz, about 3 kHz to about 5 kHz, about 3 kHz to about 4 kHz, or about 4 kHz to about 5 kHz. In other embodiments, the frequency is about 1 kHz.

[0165] In some embodiments, the electroluminescence output is characterized by a pressure of 0 kPa to about 180 kPa. In other embodiments, the pressure is 0 kPa to about 150 kPa, 0 kPa to about 100 kPa, 0 kPa to about 50 kPa, about 10 kPa to about 180 kPa, about 10 kPa to about 150 kPa, about 10 kPa to about 100 kPa, about 10 kPa to about 50 kPa, about 30 kPa to about 180 kPa, about 30 kPa to about 150 kPa, about 30 kPa to about 100 kPa, about 30 kPa to about 50 kPa, , about 50 kPa to about 180 kPa, about 50 kPa to about 150 kPa, about 50 kPa to about 100 kPa, about 100 kPa to about 180 kPa, or about 100 kPa to about 150 kPa. In other embodiments, the pressure is 0 kPa to about 30 kPa. In other embodiments, the pressure is about 30 kPa to about 180 kPa.

[0166] The sensitivity of the electroluminescence output may be modified by adjusting the voltage of the AC power supply.

[0167] In some embodiments, the electroluminescence output is characterized by a sensitivity of about 0.1 kPa-1to about 1.5 kPa-1. In other embodiments, the sensitivity is about 0.1 kPa-1to about 1.0 kPa-1, about 0.1 kPa-1to about 0.8 kPa1, about 0.1 kPa-1to about 0.5 kPa1, about 0.20 kPa1to about 1.5 kPa1, about 0.2 kPa1to about 1.0 kPa1, about 0.2 kPa1to about O.SOkPa1, about 0.2 kPa-1to about 0.5 kPa-1, about 0.5 kPa-1to about 1.5 kPa-1, about 0.5 kPa'1to about 1.0 kPa-1, about 0.5 kPa'1to about 0.8 kPa'1, or about 1 kPa'1to about 1.5 kPa1.

[0168] In some embodiments, when the sensed pressure is about 30 kPa to about 180 kPa, the device's electroluminescence output is characterized by a sensitivity is about 0.1 kPa'1to about 0.5 kPa'1. In other embodiments, the sensitivity is about 0.1 kPa1to about 0.4 kPa1, about 0.1 kPa1to about 0.3 kPa1, about 0.1 kPa'1to about 0.2 kPa'1, about 0.2 kPa'1to about 0.5 kPa'1, about 0.2 kPa'1to about 0.4 kPa'1, about 0.2 kPa'1to about 0.3 kPa'1, about 0.3 kPa'1to about 0.5 kPa'1, about 0.3 kPa'1to about 0.4 kPa'1, or about 0.4 kPa'1to about 0.5 kPa'1. In other embodiments, the sensitivity is about 0.15 kPa1.

[0169] In some embodiments, when the sensed pressure is 0 kPa to about 30 kPa, the device's electroluminescence output is characterized by a sensitivity is about 1 kPa-1to about 1.5 kPa-1. In other embodiments, the sensitivity is about 1 kPa-1to about 1.4 kPa-1, about 1 kPa-1to about 1.3 kPa-1, about 1 kPa-1to about 1.2 kPa-1, about 1.1 kPa1to about 1.5 kPa1, about 1.1 kPa1to about 1.4 kPa1, about 1.1 kPa1to about 1.3 kPa1, about 1.1 kPa1to about 1.2 kPa1, about 1.2 kPa-1to about 1.5 kPa-1, about 1.2 kPa-1to about 1.4 kPa-1, about 1.2 kPa-1to about 1.3 kPa-1, about 1.3 kPa-1to about 1.5 kPa-1, about 1.3 kPa-1to about 1.4 kPa-1, or about 1.4 kPa-1to about 1.5 kPa-1. In other embodiments, the sensitivity is about 1.12 kPa1.

[0170] The pressure sensing device may be stretchable. The presence of PEDOT: PSS / PU may enhance the connectivity and stability of the metal nanowires network. For example, the addition of PEDOT: PS5 / PU spray coated on the metal nanowires may resulted in a strain of about 45% before breakage during stretching.

[0171] In some embodiments, the device is characterized by a strain of about 30% to about 60%. In other embodiments, the strain is about 30% to about 55%, about

[0172] 30% to about 50%, about 30% to about 45%, about 35% to about 60%, about

[0173] 35% to about 55%, about 35% to about 50%, about 35% to about 45%, about

[0174] 40% to about 60%, about 40% to about 55%, about 40% to about 50%, about

[0175] 40% to about 45%, about 45% to about 60%, about 45% to about 55%, or about 45% to about 50%. In some embodiments, the strain is about 45%.

[0176] The present disclosure also concerns a method of fabricating a pressure sensing device as disclosed herein, the method comprising : a) bonding a pressure sensing layer to a surface of an electroluminescence layer such that a second polymer layer of the pressure sensing layer is contacted with the surface of the electroluminescence layer; b) bonding another surface of the electroluminescence layer with a transparent electrode layer such that the electroluminescence layer is sandwiched between the second polymer layer of the pressure sensing layer and the transparent electrode layer; and c) electrically communicating the pressure sensing layer and the transparent electrode layer.

[0177] For example, as shown in Figure 2, a polymer film is cured onto a silicon wafer with complementary microstructures, followed by coating with a solution of silver nanowires and a mixture of a layer of polymer. The silver nanowires and layer of polymer may be spray coated onto the polymer film, forming the pressure sensing layer. The transparent electrode layer is formed by coating a layer silver nanowires and a layer of polymer on a silicone rubber substrate without microstructures. The silver nanowires and layer of polymer may be spray coated. The electroluminescence layer is formed by coating a mixture of polymer and ZnS:Cu. The coating may be done by blade coating. The layers are then assembled.

[0178] In some embodiments, the bonding in step a) is performed using adhesive. In some embodiments, the adhesive is double-sided adhesive tape.

[0179] In some embodiments, the bonding in step b) is performed using adhesive. In some embodiments, the adhesive is double-sided adhesive tape.

[0180] In some embodiments, the pressure sensing layer and the transparent electrode layer are electrically communicated using a wire and / or metallic paste. In some embodiments, the pressure sensing layer and the transparent electrode layer are electrically communicated using copper wires and silver paste.

[0181] The present disclosure also concerns a method of detecting pressure, comprising : a) subjecting a pressure sensing device as disclosed herein; and b) obtaining an electroluminescence output and / or capacitance output from the pressure sensing device.

[0182] Examples

[0183] Fabrication of the pressure sensing device

[0184] The device is composed of a three-layer structure that includes a pressuresensing layer, a transparent electrode, and an electroluminescent layer that is sandwiched between them, as illustrated in Figure 1. The pressure sensing layer is constructed using photolithography to fabricate a silicon wafer with complementary microstructures that measure 20 pm in diameter, 15 pm in height, and 10 pm in spacing. A PDMS mixture consisting of base and curing agent (w / w = 10: 1) is then poured into the template and cured at 70°C for approximately 4 hours to obtain a PDMS film with microdome structures. The resulting film is subjected to treatment with tergeo plasm cleaner for 2 minutes at 15W, followed by spray-coating with a solution of silver nanowires (AgNWs) (5mg / ml; 90nm; 50pm) on a hotplate at 70°C. To enhance the stretchability and flexibility of the conductive network on the film, a mixture of PEDOT : PSS / PU is spray-coated onto it. The pressure sensing layer is then heated on a hotplate at 120°C for 30 mins. The same method is employed for the fabrication of the transparent electrode, except that the substrate used is a silicone rubber sheet without microstructures.

[0185] To create the electroluminescent layer, fluoroelastomer is mixed with acetone, followed by the addition of 50 wt% ZnS:Cu and blade-coated to form a thin film. For example, ZnS:Cu may be mixed with a 4wt% PVDF solution in a 1 : 1 ratio. Copper wires are connected to the pressure sensing layer and transparent electrode using silver paste, and the device is assembled layer by layer using double-sided adhesive tape, as shown in Figure 2, where Figure 2a shows the fabrication method of the pressure sensing layer, Figure 2b shows the fabrication method of the electroluminescent layer and Figure 2c shows the fabrication method of the transparent electrode.

[0186] Micromorphology of each component of the pressure sensing device

[0187] The micromorphology of the pressure sensing layer was examined using SEM.

[0188] The microdomes on this layer exhibit a height of 15 pm and a diameter of 20 pm, and are uniformly spaced at 10 pm, as illustrated in Figure 3a. Upon coating with AgNWs dispersion, the AgNWs become well connected and form a conductive network upon curing, as shown in Figure 3c. To further enhance the conductivity and flexibility of this layer, a PEDOT: PSS / PU solution was applied, resulting in the formation of a hybrid conductive film, as shown in Figure 3d. The top view of the layer coated with the hybrid conductive film is depicted in Figure 3b.

[0189] Figure 3a shows the side view of the microdome arrays on the pressures sensing layer. Figure 3b shows the top view of the microdome arrays coated with AgNWs and PEDOT:PSS / PU. Figure 3c shows a single dome coated with AgNWs. Figure 3d shows a single dome coated with AgNWs and PEDOT:PSS / PU.

[0190] As depicted in Figure 4a, the PVDF electroluminescent layer contains embedded ZnS:Cu phosphor particles and forms a uniform and elastic film. The porous structure of the PVDF substrate contributes to a significant change in capacitance when pressure is applied, resulting in enhanced mechanical sensitivity. Additionally, the AgNWs / PEDOT: PSS / PU film was formed on the transparent electrode, demonstrating a well-fabricated conductive layer where AgNWs were well connected to form a conductive network, and PEDOT: PSS / PU fills the interspaces to increase conductivity, as shown in Figure 4b.

[0191] Figure 4a shows ZnS:Cu particles embedded in PVDF. Figure 4b shows AgNWs / PEDOT: PSS / PU film on transparent electrode.

[0192] Capacitive response of the pressure sensing device

[0193] The E-skin features two sensing modes, capacitive response and electroluminescent response.

[0194] The capacitance of the E-skin can be formulated as:

[0195] C — soerA / d (1) where Eo represents the permittivity of the vacuum, Erdenotes the relative permittivity, A is the effective area of the electrodes, and d corresponds to the separation between the plates. When pressure is applied to the device, the microstructures on the pressure sensing layer undergo deformation. This deformation results in an increased contact area and a reduced distance between the two electrodes. The sensitivity of the capacitive response is defined as:

[0196] Sc= 8(AC / Ca) / 6P (2) where P is the applied pressure and AC and Co are the change of capacitance and initial capacitance of the device. In terms of the capacitive pressure response, the device exhibits two linear regimes when subjected to pressures ranging from 0-180 kPa. The first regime, which encompasses the low-pressure range (<30 kPa), demonstrates a sensitivity of 0.011 kPa-1. The second regime, covering the high-pressure range (30-180 kPa), displays a sensitivity of 0.002 kPa1. The response curve illustrating these sensitivities is presented in Figure 5a. The device's high sensitivity in the low-pressure regime, along with its wide sensing range, indicates its capability to detect small stimuli while also accurately measuring large stimuli across a broad range. Furthermore, the device shows high stability and flexibility, maintaining pressure-sensing performance even after 1000 bending cycles, as shown in Figure 5b.

[0197] Figure 5a shows a capacitive pressure-sensing curve. Figure 5b shows pressuresensing curves before and after 1000 bending cycles.

[0198] To evaluate the response time of the device, a sudden pressure was applied to it. The device exhibited a short response time of 110 ms to reach a stable state after the pressure was applied, as shown in Figure 6a. Upon removal of the pressure, the device quickly recovered to its original state in just 150 ms. This response and recovery time highlight the device's ability to quickly adapt to changes in pressure stimuli. Additionally, when subjected to a series of finger touches on the device, it can detect gentle finger press events with high sensitivity and a quick response, as illustrated in Figure 6b. When subjected to 4000 loading-unloading cycles at a loading rate of 10 kPa s’1, the device exhibits good cycle stability, as shown in Figure 7.

[0199] Figure 6a shows the response and recovery of the device with sudden pressure applied. Figure 6b shows finger-press events on the device.

[0200] Figure 7a shows the cycle stability of the device after 4000 loading-unloading cycles. Figure 7b shows an enlarged view of the cycle stability graph in Figure 7a.

[0201] Electroluminescent response of the pressure sensing device

[0202] When connected to a high-voltage AC power supply, the device's optical particles ZnS:Cu within the electroluminescent layer generate luminescence that is proportional to the local electric field intensity. The pressure applied to the device causes a decrease in the distance between the pressure sensing layer and the transparent electrode, resulting in an increase in the electric field intensity. This change in electric field intensity contributes to the modulation of luminescence in response to varying pressure levels.

[0203] The frequency of the power supply, in addition to the voltage and applied pressure, also plays a role in influencing the intensity of electroluminescence. When the voltage is fixed at 100 V and the pressure is maintained at 30 kPa, the luminescent intensity exhibits an increasing trend as the frequency is raised from 0 to 5 kHz. Notably, when the frequency is increased from 0 to 1 kHz, the luminescent intensity shows a significant increase, as shown in Figure 8. However, beyond 1 kHz, the rate of increase in luminescent intensity becomes relatively lower, accompanied by higher power consumption and louder noise. It was determined that 0-1 kHz is the optimal working frequency for the device as the rate of change of luminescent is more significant while maintaining a balance between power consumption and noise levels.

[0204] To investigate the luminescent pressure sensing performance of the device, increasing pressure ranging from 0-180 kPa with voltage ranging from 100- 250 V and a working frequency of 1 kHz was applied. The results indicate that the device has high sensitivity for luminescent response in the low-pressure range of 0-30 kPa. However, beyond 30 kPa, the sensitivity decreases, as shown in the results. The sensitivity of luminescent response is defined as:

[0205] SL= ai L / L^ / SP (3) where P denotes the applied pressure and AL and Lo are the change of luminescence and initial luminescence of the device respectively. As shown in Figure 9, it can be observed that with an increasing voltage of the AC power supply, the slope of the sensing curve increases, indicating an increase in the sensitivity of the device. Therefore, the sensitivity can be modified by adjusting the voltage of the AC power supply.

[0206] The device exhibits a short response time for luminescent response. To test the luminescent change, a penpoint was pressed onto the device, and the luminescence was recorded using a camera. As shown in Figure 10, after pressing the penpoint, the pressed site took approximately 30 ms to reach the highest luminescent intensity. After removing the penpoint, the device took another 30 ms to fade completely.

[0207] Overall, the E-skin demonstrates good sensing performance for dual sensing modes, making it suitable for various application scenarios.

[0208] Pressure mapping with high spatial resolution

[0209] The device may be able to achieve high-resolution pressure mapping, such as fingerprints, with minimal distortions. When a patterned pressure is exerted on the non-conductive side of the pressure-sensing layer of the device (i.e. on the external facing surface of the first polymer layer), the pressure distribution is transferred between the pressure sensing layer and the electroluminescent layer, leading to an increase in electrical field and the intensity of luminescence at the pressure applying site. The resolution is characterized by pressing pillar arrays with different densities onto the device. Two different thicknesses of pressure-sensing layers were tested for comparison (200 pm and 10 pm).

[0210] The device with the 200 pm-thick pressure sensing layer exhibits lower mapping resolution, which can only distinguish the pillar array with a radius of 400 pm and a gap of 400 pm, but not a pillar array with a radius of 200 pm and a gap of 200 pm, nor fingerprints, as shown in Figure I la. However, with a 10 pm- thick pressure sensing layer, the device can identify both pillar arrays and fingerprints, as illustrated in Figure lib. These results demonstrate the device's high potential for high-resolution pressure mapping applications.

[0211] To mimic the pressure-sensing function of human skin, the device's ability extends beyond the detection of static pressure to include dynamic stimuli. This is demonstrated by writing the letter "L" on the device with a brush pen. The trace was recorded at 0.5 s intervals, as shown in Figure 12. By assembling the traces, the letter "L" was clearly demonstrated. This dynamic sensing capability highlights the potential for the device to be used in applications such as haptic feedback and prosthetic limbs.

[0212] For high-resolution pressure mapping, the image of the fingerprint luminescent distribution on the device was captured. For the region in the dotted box, the pixel intensity was calculated, which shows not only the spatial details but also the relative magnitude of pressure, as shown in Figure 13. This method allows for quantitative analysis of the pressure distribution and can be used to provide feedback in applications such as touchscreens and robotics.

[0213] Biomedical application - foot pressure mapping

[0214] Pressure mapping is widely used in various healthcare scenarios, including foot pressure mapping. A proposed device for pressure mapping is shown in Figure 14. When people stand on the device, the luminescence can be reflected by the mirror, which can be easily observed by the human eye or captured by a camera for further signal processing. This method provides a non-invasive and convenient way to analyse the pressure distribution on the feet, which can aid in the diagnosis and treatment of various foot-related conditions.

[0215] A 3D-printed model foot was applied to the pressure sensing device with a size of 4 cm x 4 cm. The AC power supply had a voltage of 150 V and a frequency of 1 kHz. The luminescent distribution was captured and is shown in Figure 15b. To obtain the pressure distribution, a curve was created by capturing the image of the luminescence distribution when a 1 cm x 1 cm 3D-printing stamp was applied to the device with different pressures and then the corresponding mean pixel intensity was calculated, as shown in Figure 15a. The pixel intensity distribution in Figure 15c was calculated from the raw image captured by the camera. Using the converting curve of the relationship between pressure and luminescence, a pressure distribution of the model foot was generated, as shown in Figure 15d. These results demonstrate the potential for the pressure sensing device to be used in pressure mapping applications for various anatomical structures.

[0216] Figure 15a shows the relationship between pixel intensity and applied pressure. Figure 15b shows the luminescent image of foot model pressing on the device. Figure 15c shows the distribution of pixel intensities in the image presented in Figure 15b. Figure 15d shows the pressure mapping derived from Figure 15c utilizing the characteristic curve depicted in Figure 15a.

[0217] Stretchabilitv of the pressure sensing device

[0218] To evaluate the stretchability of the pressure sensing device, the inventors fabricated transparent electrodes coated with AgNWs and varying amounts of spray coated PEDOT:PSS / PU, then subjected them to testing using a tensile tester as depicted in Figure 16a. The size of the electrode is 2 cm x 2 cm, and 50 mL or 100 mL of PEDOT: PSS / PU was spray coated on the electrode. The corresponding results are illustrated in Figure 16b. Initially, with AgNWs alone, the electrode exhibited weak interconnection and slight overlap of the AgNWs. The introduction of PEDOT: PSS / PU enhanced the connectivity and stability of the AgNWs network. With the addition of 50ml PEDOT: PSS / PU, a partially formed film resulted in partial coverage of the electrode and a stretched strain of about 8%. Employing 100ml PEDOT: PSS / PU yielded completely formed film

[0219] (about 200 to 600 nm thick) and an electrode that remained intact until stretched to a strain of 45%, demonstrating excellent stretchability.

[0220] It will be appreciated that many further modifications and permutations of various aspects of the described embodiments are possible. Accordingly, the described aspects are intended to embrace all such alterations, modifications, and variations that fall within the spirit and scope of the appended claims.

[0221] Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0222] Throughout this specification and the claims which follow, unless the context requires otherwise, the phrase "consisting essentially of", and variations such as "consists essentially of" will be understood to indicate that the recited element(s) is / a re essential i.e. necessary elements of the invention. The phrase allows for the presence of other non-recited elements which do not materially affect the characteristics of the invention but excludes additional unspecified elements which would affect the basic and novel characteristics of the method defined.

[0223] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Claims

Claims1. A pressure sensing device, comprising: a) a pressure sensing layer comprising a first polymer layer and a second polymer layer, the first polymer layer comprising microstructures on a first surface thereof, the second polymer layer adjacent to the microstructures on the first surface; b) a transparent electrode layer configured to be electrically conductive; c) an electroluminescence layer comprising luminescent particles, the electroluminescence layer sandwiched between the second polymer layer of the pressure sensing layer and the transparent electrode layer; wherein the pressure sensing layer is in electrical communication with the transparent electrode layer; wherein the microstructures are configured to be electrically responsive to changes in their morphologies; and wherein the electroluminescence layer is configured to provide an electroluminescence output and the transparent electrode layer is configured to produce a capacitance output in response to a pressure sensed at the pressure sensing layer.

2. The device according to claim 1, wherein the microstructures is an array of microdomes.

3. The device according to claim 1 or 2, wherein the microstructures are characterized by a diameter of about 10 pm to about 40 pm, and / or a height of about 5 pm to about 30 pm.

4. The device according to any one of claims 1 to 3, wherein the microstructures are characterized by a spacing of about 5 pm to about 20 pm.

5. The device according to any one of claims 1 to 4, wherein the first polymer layer is formed from PDMS.

6. The device according to any one of claims 1 to 5, wherein the first polymer layer is characterized by a thickness of about 5 pm to about 250 pm.

7. The device according to any one of claims 1 to 6, wherein the second polymer layer is formed from a combination of PEDOT: PSS and PU at a weight ratio of about 1: 1 to about 3: 1.

8. The device according to any one of claims 1 to 7, wherein the first polymer layer is bonded to the second polymer layer via electrostatic interaction and / or Van de Waals interaction.

9. The device according to any one of claims 1 to 8, wherein the second polymer layer is characterized by a thickness of about 500 nm to about 1000 nm.

10. The device according to any one of claims 1 to 9, wherein the pressure sensing layer further comprises metal nanowires homogenously dispersed within the first polymer layer, homogenously dispersed within the second polymer layer or layered adjacent to the microstructures.

11. The device according to claim 10, wherein the metal nanowires in the pressure sensing layer is characterized by a loading wt% of about 20 wt% to about 60 wt%.

12. The device according to any one of claims 1 to 11, wherein the pressure sensing layer is characterized by a thickness of about 10 pm to about 280 pm.

13. The device according to any one of claims 1 to 12, wherein the transparent electrode layer comprises a third polymer layer and a fourth polymer layer adjacent to the third polymer layer.

14. The device according to claim 13, wherein the third polymer layer is formed from PDMS.

15. The device according to claims 13 or 14, wherein the third polymer layer is characterized by a thickness of about 5 pm to about 250 pm.

16. The device according to any one of claims 13 to 15, wherein the fourth polymer layer is formed from a combination of PEDOT: PSS and PU at a weight ratio of about 1: 1 to about 3: 1.

17. The device according to any one of claims 13 to 16, wherein the third polymer layer is bonded to the fourth polymer layer via electrostatic interaction and / or Van de Waals interaction.

18. The device according to any one of claims 13 to 17, wherein the fourth polymer layer is characterized by a thickness of about 500 nm to about 1000 nm.

19. The device according to any one of claims 13 to 18, wherein the transparent electrode layer further comprises metal nanowires homogenously dispersed within the third polymer layer, homogenously dispersed within the fourth polymer layer or layered between the third polymer layer and the fourth polymer layer.

20. The device according to claim 19, wherein the metal nanowires in the transparent electrode layer is characterized by a loading wt% of about 20 wt% to about 60 wt%.

21. The device according to any one of claims 1 to 20, wherein the transparent electrode layer is characterized by a thickness of about 5 pm to about 250 pm.

22. The device according to any one of claims 1 to 21, wherein the electroluminescence layer further comprises a fluoroelastomer.

23. The device according to claim 22, wherein the fluoroelastomer is PVDF.

24. The device according to any one of claims 1 to 4423 wherein the luminescent particles are homogenously dispersed within the electroluminescence layer or layered adjacent to a surface of the electroluminescence layer.

25. The device according to any one of claims 1 to 24, wherein the luminescent particles is selected from ZnS:Cu, ZnS: Mn, ZnS:TbF3, ZnS:SmFs, CaS:Ce and their doped derivative thereof.

26. The device according to any one of claims 1 to 25, wherein the electroluminescence layer is characterized by a luminescent particle concentration of about 25 wt% to 75 wt%.

27. The device according to any one of claims 1 to 26, wherein the electroluminescence layer is characterized by a thickness of about 40 m to about 120 pm.

28. The device according to any one of claims 1 to 27, wherein the layers are adhesively bonded to each other.

29. The device according to any one of claims 1 to 28, wherein the pressure sensing layer and the transparent electrode layer are in electrical communication via wires.

30. The device according to any one of claims 1 to 29, wherein the microstructures are configured to deform under pressure.

31. The device according to any one of claims 1 to 30, wherein the capacitance output is characterized by a pressure of 0 kPa to about 180 kPa.

32. The device according to any one of claims 1 to 31, wherein the capacitance output response is characterized by a sensitivity of about 0.001 kPa-1to about 0.05 kPa-1.

33. The device according to any one of claims 1 to 32, wherein the device is configured to be powered by an alternating current power supply of about 100 V to about 250 V.

34. The device according to any one of claims 1 to 33, wherein the electroluminescence output is characterized by a frequency of 0 kHz to about 5 kHz.

35. The device according to any one of claims 1 to 34, wherein the electroluminescence output is characterized by a pressure of 0 kPa to about 180 kPa.

36. The device according to any one of claims 1 to 35, wherein the electroluminescence output is characterized by a sensitivity of about 0.1 kPa1to about 1.5 kPa-1.

37. The device according to any one of claims 1 to 36, wherein the device is characterized by a strain of about 30% to about 55%.

38. A method of fabricating a pressure sensing device according to any one of claims 1 to 37, comprising : a) bonding a pressure sensing layer to a surface of an electroluminescence layer such that a second polymer layer of the pressure sensing layer is contacted with the surface of the electroluminescence layer; b) bonding another surface of the electroluminescence layer with atransparent electrode layer such that the electroluminescence layer is sandwiched between the second polymer layer of the pressure sensing layer and the transparent electrode layer; and c) electrically communicating the pressure sensing layer and the transparent electrode layer.

39. The method according to claim 38, wherein the bonding in step a) and / or step b) are performed using adhesive.

40. The method according to claim 38 or 39, wherein pressure sensing layer and the transparent electrode layer are electrically communicated using a wire and / or metallic paste.

41. A method of detecting pressure, comprising: a) subjecting a pressure sensing device according to any one of claims 1 to 37 to the pressure; and b) obtaining an electroluminescence output and / or capacitance output from the pressure sensing device.

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